Regenerative type refrigerator

ABSTRACT

A disclosed regenerative type refrigerator includes a cylinder expanding a refrigerant gas; a regenerator accumulating cold thermal energy and being provided inside the cylinder so as to be reciprocate inside the cylinder; a rotary drive portion generating driving force; a rotary member being rotated by the rotary drive portion; and a bearing member supporting the rotary member and including an inner wheel, an outer wheel, and two sealing members encapsulating a lubricant agent and being provided on sides of the outer wheel and the inner wheel, wherein the sealing members are fixed to one of the inner wheel member and the outer wheel member, and a gap is formed between the two sealing members and another one of the inner wheel member and the outer wheel member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based upon and claims the benefit of priority of Japanese Patent Application No. 2011-132506 filed on Jun. 14, 2011, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a regenerative type refrigerator which stores cold thermal energy generated by expanding a refrigerant gas in a regenerator.

2. Description of the Related Art

A cryogenic refrigerator for acquiring an ultralow temperature of about 4 K is, for example, a Gifford-McMahon (GM) refrigerator.

The GM refrigerator supplies a refrigerant gas made of, for example, a helium gas supplied from a compressor to an expansion space which is formed inside a cylinder. The supplied refrigerant gas is expanded inside an expansion space to thereby generate cold thermal energy.

Stages of the GM refrigerator includes a cylinder and a displacer attached inside the cylinder. The displacer is provided inside the cylinder so that the displacer is capable of reciprocating inside the cylinder. The expansion space is formed between an end of the displacer and the cylinder. Inside the displacer, a refrigerant gas flow path is formed to supply the refrigerant gas into the expansion space and eject the refrigerant gas from the expansion space. The refrigerant gas flow path formed inside the displacer accommodates a regenerative material for accumulating cold thermal energy by contacting the refrigerant gas.

For example, a GM refrigerator disclosed in Patent Document 1 includes a motor, a crank member, and a scotch yoke. The GM refrigerator includes a rotary valve device for switching connection with a cylinder to a high pressure side or a low pressure side.

-   [Patent Document 1] Japanese Laid-open Patent Publication No.     2007-205581

An exemplary GM refrigerator includes a bearing member for supporting a rotational shaft of a motor so that the rotational shaft is rotatable, a bearing member provided between a crank member and a scotch yoke, a bearing member for supporting a valve body of a rotary valve device so that the valve body is rotatable, or another bearing member.

These bearing members may include an inner wheel, an outer wheel, a roller and a holder. The inner wheel and the outer wheel are rotatable around a single rotational axis without mutually restricting rotational motions of the inner and outer wheels. Said differently, the inner wheel and the outer wheel are relatively and freely rotatable. Rolling elements having a spherical shape are provided at equal intervals along a periphery around the rotational axis. The rolling elements are held by a holder.

The bearing member has two sealing members for encapsulating a lubricant agent within an internal space formed between both sides of the inner and outer wheels. The two sealing members are arranged along the rotational axis so as to face each other. The lubricant agent is encapsulated in the internal space surrounded by the inner wheel, the outer wheel, and the two sealing members. The two sealing members are fixed to the outer wheel.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a regenerative type refrigerator including: a cylinder configured to expand a refrigerant gas; a regenerator configured to accumulate cold thermal energy which is generated along with the expansion of the refrigerant gas, the regenerator being provided inside the cylinder so as to be reciprocate inside the cylinder and accommodating a regenerative material inside the regenerator; a rotary drive portion configured to generate driving force for reciprocating the regenerator; a rotary member configured to be rotated by the rotary drive portion; and a bearing member configured to support the rotary member so that the rotary member is rotatable, the bearing member including an inner wheel, an outer wheel, and two sealing members, the inner wheel, the outer wheel and the two sealing members encapsulating a lubricant agent among the inner wheel, the outer wheel and the two sealing members, the outer wheel and the inner wheel being relatively and freely rotatable around a single rotational axis, the two sealing members being respectively provided on sides of the outer wheel and the inner wheel and arranged along the rotational axis, wherein the two sealing members are fixed to one of the inner wheel member and the outer wheel member, and a gap is formed between the two sealing members and another one of the inner wheel member and the outer wheel member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a GM refrigerator of an embodiment;

FIG. 2 is an enlarged perspective view of a bearing member;

FIG. 3 is an exploded perspective view of a scotch yoke mechanism;

FIG. 4 is an exploded perspective view of a rotary valve device;

FIG. 5 is a cross-sectional view of a bearing member;

FIG. 6 is a cross-sectional view of a GM refrigerator of a comparative example 1; and

FIG. 7 is a cross-sectional view of a GM refrigerator of a comparative example 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description is given below, with reference to the FIG. 1 through FIG. 7 of embodiments of the present invention.

In order to encapsulating the lubricant agent, the sealing member contacts the inner wheel. The internal space surrounded by the inner wheel, the outer wheel and the two sealing members may have airtightness so as to separate the internal space from an outer space of the internal space. The outer pressure of the bearing member greatly varies when the cylinder is switched between the high pressure side and the low pressure side of the compressor by the rotary valve device. A large pressure difference may be generated between the internal space of the bearing member and the outer space along with the pressure variation of the outer space of the bearing member. Then, the sealing members may receive large force thereby being apt to be deformed.

The above problem may occur not only in GM refrigerators but also various regenerative type refrigerators including regenerators which include regenerative material and accumulate cold thermal energy generated by expanding a refrigerant gas.

Accordingly, embodiments of the present invention may provide a novel and useful regenerative type refrigerator solving one or more of the problems discussed above. More specifically, the embodiments of the present invention may provide a regenerative type refrigerator which can reduce an outlet amount of the lubricant agent from the internal space of the bearing member, can reduce a mixed amount of an extraneous material into the internal space of the bearing member, and can prevent deformation of the sealing members of the bearing member.

Additional objects and advantages of the embodiments are set forth in part in the description which follows, and in part will become obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed.

Embodiment

Referring to FIG. 1, a GM refrigerator is exemplified as a regenerative type refrigerator of the embodiment. The GM refrigerator has a two stage structure suitable for acquiring an ultralow temperature of about several K to 20 K.

FIG. 1 is a cross-sectional view of a GM refrigerator of the embodiment. FIG. 2 is an enlarged perspective view of a bearing member 60. FIG. 3 is an exploded perspective view of a scotch yoke mechanism 32. FIG. 4 is an exploded perspective view of a rotary valve device 40.

The GM refrigerator includes a compressor 1, a cylinder unit 2, and a housing unit 3.

The compressor 1 suctions a refrigerant gas (helium gas) from a low pressure side 1 a. After compressing the suctioned refrigerant gas so as to increase the pressure of the suctioned gas and simultaneously cooling the suctioned gas, the refrigerant gas is discharged to a high pressure side 1 b. The pressure of the high pressure side 1 b is about 2 MPa, and the pressure of the low pressure side 1 a is about 0.5 MPa.

The cylinder unit 2 includes a first stage cylinder 11, a second stage cylinder 12, a first stage displacer 13, a second stage displacer 14, internal spaces 15 and 16, and regenerative materials 17 and 18.

The first stage cylinder 11 and the second stage cylinder 12 are arranged in a horizontal direction to have a two-tiered structure. The first stage displacer 13 and the second stage displacer 14 are provided inside the first stage cylinder 11 and the second stage cylinder 12 so as to be capable of reciprocating and sliding inside the first stage cylinder 11 and the second stage cylinder 12, respectively.

Expansion spaces 21, 22 and 23 are formed among the first stage displacer 13, the second stage displacer 14, the first stage cylinder 11 and the second stage cylinder 12. For example, the expansion space 23 is formed between the first stage cylinder 11 and the first stage displacer 13, the expansion space 21 is formed between the first stage cylinder 11 and the second stage displacer 14, and the expansion space 22 is formed between the second stage cylinder 12 and the second stage displacer 14. The internal space 15 is formed inside the first stage displacer 13. The internal space 16 is formed inside the second stage displacer 14. The regenerative materials 17 and 18 are accommodated inside the internal spaces 15 and 16.

Refrigerant gas flow paths L1 to L4 are formed inside the first stage displacer 13 and the second stage displacer 14 and connect the expansion spaces 21, 22, and 23. For example, the first stage displacer 13 has the refrigerant gas flow paths L1-L3, and the second stage displacer 14 has the refrigerant gas flow paths L4. Accordingly, the internal spaces 15 and 16 function as refrigerant gas flow paths for supplying the refrigerant gas to the expansion spaces 21, 22 and 23 and for ejecting the refrigerant gas from the expansion spaces 21, 22 and 23.

A flange 19 is formed on a lower peripheral portion of the first stage cylinder 11 so as to thermally couple the first stage cylinder 11 to the flange 19. A flange 20 is formed on a lower peripheral portion of the second stage cylinder 12 so as to thermally couple the second stage cylinder 12 to the flange 20.

As described later, the first stage displacer 13 and the second stage displacer 14 accumulate cold thermal energy, which is generated by expansion of the refrigerant gas in the expansion spaces 21 and 22, in the regenerative materials 17 and 18. The first stage displacer 13 and the second stage displacer 14 may correspond to a regenerator recited in claims.

Referring to FIG. 1, the housing unit 3 includes a drive device 30 and a rotary valve device 40.

The drive device 30 includes a motor 31 and a scotch yoke mechanism 32. The motor 31 generates rotary drive force. The motor 31 may correspond to a rotary drive portion of the embodiment.

Referring to FIG. 1, the rotational shaft 31 a of the motor 31 is rotatably supported by the bearing members 60, which are provided on both side of the rotational shaft 31 a. Referring to FIG. 2, the bearing member 60 includes an inner wheel 61, an outer wheel 62, and a sealing member 63. The inner wheel 61 and the outer wheel 62 are rotatable around a single rotational axis without mutually restricting rotational motions of the inner and outer wheels 61 and 62. Said differently, the inner wheel 61 and the outer wheel 62 are relatively and freely rotatable. The sealing member 63 is fixed to the outer wheel 62 and is provided to form a gap P between the sealing member 63 and the inner wheel 61. The inner wheel 61 is fixed to the rotational axis shaft 31 a. A detailed structure of the bearing member 60 is described later with reference to FIG. 5.

Referring to FIG. 3, the scotch yoke mechanism 32 includes a crank member 33 and a scotch yoke 34. The scotch yoke mechanism 32 converts rotary drive force generated by the motor 31 to reciprocating drive force thereby reciprocating the first stage displacer 13 and the second stage displacer 14.

The crank member 33 is fixed to the rotational shaft 31 a of the motor 31 and driven by the motor 31. The crank member 33 has a crankpin 33 b at an eccentric position from the rotational shaft 31 a of the motor 31. After attaching the crank member 33 to the rotational shaft 31 a of the motor 31, the rotational shaft 31 a and the crankpin 33 b become eccentric.

The scotch yoke 34 includes a yoke plate 35, a vertical shaft 36 and a bearing member 60A. The scotch yoke 34 is capable of reciprocating inside the housing unit 3 in directions Z1 and Z2 in FIG. 1 and FIG. 3. At a center of the yoke plate 35, the vertical shaft 36 is formed to protrude on the vertical directions Z1 and Z2. The vertical shaft 36 is supported by slide bearings 38 a and 38 b in the vertical directions Z1 and Z2.

The yoke plate 35 has an ellipse opening 35 a extending in the directions X1 and X2 in FIG. 3. The bearing member 60A is inserted into the ellipse opening 35 a. The bearing member 60A is movable inside the ellipse opening 35 a in directions of arrows X1 and X2.

The bearing member 60A includes the inner and outer wheels 61 and 62 relatively and freely rotatable, and the sealing member 63. The bearing member 60A is formed in a manner similar to that in the bearing member 60. The sealing member 63 is fixed to the outer wheel 62 and is provided to form a gap G between the sealing member 63 and the inner wheel 61. The inner wheel 61 is fixed to the crankpin 33 b. A detailed structure of the bearing member 60A is described later together with the detailed structure of the bearing member 60A with reference to FIG. 5.

If the rotational shaft 31 a is rotated while the crankpin 33 b is fixed to the bearing member 60A, the crankpin 33 b is eccentrically rotated so as to trace a trajectory of a circular arc thereby reciprocating the scotch yoke 34 in the directions of the arrows Z1 and Z2 in FIG. 3. At this time, the bearing member 60A reciprocates inside the ellipse opening 35 a in the directions of the arrows X1 and X2 in FIG. 3.

A portion of the vertical shaft 36 provided below the scotch yoke 34 is connected to the first stage displacer 13. Therefore, the scotch yoke 34 reciprocates along with the first stage displacer 13 in the directions Z1 and Z2 in FIG. 1.

Movement of the crankpin 33 b of the crank member 33 in directions Y1 and Y2 along the axis of the crankpin 33 b is restricted. Movement of the scotch yoke 34 in the directions Y1 and Y2 along the axis of the crankpin 33 b is also restricted.

The crankpin 33 b may correspond to a crank member recited in the claims.

Referring to FIG. 1, the rotary valve device 40 is provided between the compressor 1 and the first stage cylinder 11 (the second stage cylinder 12). The rotary valve device 40 is to control flow of the refrigerant gas. Specifically, the rotary valve device 40 may switch the connection of the first stage cylinder 11 and the second stage cylinder 12 to the high pressure side 1 b of the compressor 1. The refrigerant gas discharged from the high pressure side 1 b of the compressor 1 is suctioned into the first stage cylinder 11 and the second stage cylinder 12. The rotary valve device 40 may switch the connection of the first stage cylinder 11 and the second stage cylinder 12 to the low pressure side 1 a of the compressor 1. The refrigerant gas ejected from the first stage cylinder 11 and the second stage cylinder 12 passes through a space 4 and a low pressure pipe 5, which is provided above the housing unit 3 and connected to the space 4, is suctioned by the low pressure side 1 a of the compressor 1. By repeating the above-described actions, the rotary valve device 40 switches the connection of the first stage cylinder 11 and the second stage cylinder 12 to the low pressure side 1 a or the high pressure side 1 b of the compressor 1. The low pressure side 1 a of the compressor 1 may correspond to a suction side recited in the claims, and the high pressure side 1 b of the compressor 1 may correspond to a discharge side recited in the claims.

Referring to FIG. 1 and FIG. 4, the rotary valve device 40 includes a valve body 41 and a valve plate 42. The valve body 41 and the valve plate 42 include flat surfaces, respectively. The flat surfaces of the valve body 41 and the valve plate 42 mutually contact face to face.

The valve body 41 is fixed by a fixing pin 43 to an inside of the housing unit 3. Meanwhile, referring to FIG. 4, the valve plate 42 is engaged with a tip of the crankpin 33 b so that the valve plate 42 rotates when the crankpin 33 b rotates around the crankshaft 33 a and the rotational shaft 31 a of the motor 31.

Referring to FIG. 1 and FIG. 4, the valve plate 42 is rotatably supported by a bearing member 60B. The bearing member 60B includes inner and outer wheels 61 and 62 relatively and freely rotatable and a sealing member 63. The bearing member 603 is formed in a manner similar to that in the above-described bearing member 60. The sealing member 63 is fixed to the outer wheel 62 and is provided to form a gap G between the sealing member 63 and the inner wheel 61. The inner wheel 61 is fixed to the valve plate 42. A detailed structure of the bearing member 60B is described later together with the detailed structure of the bearing member 60 with reference to FIG. 5.

Referring to FIG. 4, the bearing member 60B is indicated by a dot-line for facilitating illustration. The valve plate 42 may correspond to a rotary valve recited in the claims.

A refrigerant gas suction port 44 penetrates the valve body 41 at a center of the valve body 41. The refrigerant gas suction port 44 is connected to the high pressure side 1 b of the compressor 1. Referring to FIG. 4, an arc-like groove 46 shaped like a circular arc along a circle around an axis (a middle of a circle) of the refrigerant gas suction port 44 is formed on an end surface 45 of the valve body 41. A through-hole 48 is formed in the valve body 41. One end of the through-hole 48 is opened inside the arc-like groove 46 and the other end of the through-hole 48 is opened on a side surface of the valve body 41 as a discharge port. The discharge port 47 communicates with the expansion space 23 via a passage 49 (see FIG. 1).

A groove 51 extending from a center of an end surface 50 of the valve plate 42 facing the valve body 41 in a radius direction is formed on the end surface 50 of the valve plate 42 facing the valve body 41. An arc-like hole 53 is formed to penetrate the end surface 50 of the valve plate 42 facing the valve body 41 to the other end surface 52 opposite to the end surface 50. The arc-like hole 53 is positioned along the circumference of the circle for the arc-like groove 46 around the center of the refrigerant gas suction port.

A suction valve is formed by the refrigerant gas suction port 44, the groove 51, the arc-like groove 46, and the through-hole 48. An ejection valve is formed by the through-hole 48, the arc-like groove 46, and the arc-like hole 53.

While the scotch yoke 34 reciprocates in the directions Z1 and Z2, the first stage displacer 13 and the second stage displacer 14 reciprocate in the directions Z1 and Z2 so as to move inside the first stage cylinder 11 (for the first stage displacer 13) and the second stage cylinder 12 (for the first stage displacer 14) between a lower dead center LP and an upper dead center UP.

When the first stage displacer 13 and the second stage displacer 14 reach the lower dead center LP, the ejection valve is closed and a refrigerant gas flow path is formed by the through-hole 48, the arc-like groove 46, and the groove 51. The high pressure refrigerant gas starts to flow into the expansion space 23 via the passage 49 inside the housing unit 3. Thereafter, the first stage displacer 13 and the second stage displacer 14 starts to rise after reaching the lower dead center LP. The refrigerant gas downward passes through the regenerative material 17 and 18 so as to be supplied to the expansion spaces 21 and 22. Thus, the expansion spaces 21 and 22 are filled with the refrigerant gas.

When the first stage displacer 13 and the second stage displacer 14 reach the upper dead center UP, the suction valve is closed and a refrigerant gas flow path is formed by the through-hole 48, the arc-like groove 46, and the arc-like hole 53. The high pressure refrigerant gas generates cold thermal energy by adiabatic expansion. The generated cold thermal energy cools the flanges 19 and 20 while upward passing through the regenerative materials 17 and 18. Then, the refrigerant gas passes through the space 4 and the low pressure pipe 5 and starts to flow on the lower pressure side 1 a of the compressor 1. The generated cool thermal energy is accumulated by the regenerative materials 17 and 18.

Thereafter, when the first stage displacer 13 and the second stage displacer 14 reaches the lower dead center LP, the ejection valve is closed and the suction valve is opened to thereby complete one cycle. As described, by repeating cycles including the compression and the expansion of the refrigerant gas, the refrigerator generates the cold thermal energy and accumulates the generated cold thermal energy.

Instead of the rotary valve device 40, a switching device formed by the suction valve and the ejection valve may be provided on the side of the compressor 1 outside the housing unit 3. The compressor 1 and the expansion spaces 21 to 23 may be connected using the switching device, which can switch over connections by the suction valve and the ejection valve in synchronism with the reciprocating motion of the first stage displacer 13 and the second stage displacer 14. While reciprocating the first stage displacer 13 and the second stage displacer 14, the switching device can repeat the cycles of compression and expansion of the refrigerant gas by switching over the connection between the expansion space 21 to 23 and the low pressure side 1 a or the high pressure side 1 b of the compressor 1. At this time, the bearing member 60B is not provided.

The structure of the bearing members 60, 60A, and 60B is described. Hereinafter, the bearing member 60 is described as a representative of the bearing members 60, 60A, and 60B. Therefore, the bearing members 60A, and 60B may employ a structure similar to the following.

FIG. 5 is a cross-sectional view of the bearing member 60. Referring to FIG. 5, a part of the rotational axis shaft 31 a fixed to the inner wheel 61 is also illustrated. However, in the bearing member 60A, the crankpin 33 b is fixed to the inner wheel 61 instead of the rotational axis shaft 31 a. In the bearing member 60B, the valve plate 42 is fixed to the inner wheel 61 instead of the rotational axis shaft 31 a.

Referring to FIG. 5, the bearing member 60 includes the inner wheel 61, the outer wheel 62, the sealing member 63, a rolling element 64, and a holder 65.

The inner wheel 61 may correspond to an inner wheel recited in the claims. The outer wheel 62 may correspond to an outer wheel recited in the claims.

The inner wheel 61 and the outer wheel 62 are rotatable around a single rotational axis RA without mutually restricting rotational motions of the inner and outer wheels. Said differently, the inner wheel and the outer wheel are relatively and freely rotatable around the rotational axis RA. The inner wheel 61 is assembled inside the outer wheel 62.

The rolling element 64 for relatively and freely rotating the inner wheel 61 and the outer wheel 62 is provided between the inner peripheral surface of the outer wheel 62 and the outer peripheral surface of the inner wheel 61. The rolling element 64 may be a ball bearing in a spherical shape, a needle bearing in a cylindrical shape, or the like. The holder 65 is provided to hold the rolling members 64 while maintaining gaps among the rolling members 64 along a peripheral direction around the rotational axis shaft RA to have a predetermined value.

Referring to FIG. 1 and FIG. 2, the inner wheel 61 is fixed to the rotational axis shaft 31 a. On the other hand, the outer housing 62 is fixed to the housing unit 3 of the GM refrigerator. Therefore, the bearing member 60 made of the inner wheel 61 and the outer wheel 62 supports the rotational shaft 31 a so that the rotational shaft 31 a is rotatable.

The material of the inner wheel 61, the outer wheel 62, the rolling element 64, and the holder 65 may be obtained by providing a thermosetting process to martensitic stainless steel ferritic stainless steel such as SUS440C, may be precipitation hardening stainless steel such as SUS630, and may be obtained by providing a surface hardening process to austenitic stainless steel such as SUS316, fro example.

Inside the internal space S formed between the inner wheel 61 and the outer wheel 62, a lubricant agent made of, for example, grease is enclosed. The sealing members 631 and 632 are provided on both sides (the left and right sides in FIG. 5) of the inner wheel 61 and the outer wheel 62 along the rotational axis RA. The sealing members 631 and 632 are used to encapsulate the lubricant agent between the inner wheel 61 and the outer wheel 62.

The sealing members 631 and 632 are fixed to the outer wheel 62. The sealing members 631 and 632 are fixed to the outer wheel 62 by, for example, a bond along the peripheral direction around the rotational axis RA. A gap is not formed between the outer wheel 62 and the sealing members 631 and 632. On the other hand, the sealing members 631 and 632 are not fixed to the inner wheel 61. The sealing members 631 and 632 are formed along the peripheral direction around the rotational shaft RA so that the gap G is formed between the inner wheel and the sealing members 631 and 632. Therefore, it is possible to reduce the amount of the lubricant agent which flows out of the internal space S, to reduce the amount of an extraneous material intruding into the internal space S, and to prevent the sealing members 631 and 632 from deforming.

Referring to comparative examples 1 and 2, effects and functions in the reduction of the amount of the lubricant agent which flows out of the internal space S, the reduction of the amount of the extraneous material intruding into the internal space S, and the prevention of the deformation of the sealing members 631 and 632 are described.

FIG. 6 is a cross-sectional view of a bearing member 60 a of a GM refrigerator of the comparative example 1. FIG. 7 is a cross-sectional view of a bearing member 60 b of GM refrigerator of the comparative example 2.

Within the comparative example 1, a sealing member is not formed on the bearing member 60 a. Instead of the sealing member, shield plates 631 a and 632 a made of a steel plate are provided. The shield plates 631 a and 632 a are separated from the inner wheel 61. Therefore, there is no function of sealing a lubricant agent. Therefore, the amount of the lubricant agent passing through a gap LG between the shield plates 631 a and 632 a and the inner wheel 61, and flowing out of an internal space S increases. Further, the amount of extraneous materials generated from various sliding portions of the GM refrigerator, passing through the gap LG between the shield plates 631 a and 632 a and the inner wheel 61, and intruding into the internal space S increases.

Within the comparative example 2, sealing members 631 b and 632 b are formed on the bearing member 60 b, and there is no gap between an inner wheel 61 and sealing members 631 b and 632 b, said differently, the inner wheel 61 contacts the sealing members 631 b and 632 b. Therefore, an internal space S surrounded by the inner wheel 61, an outer wheel 62, and the two sealing members 631 b and 632 b has airtightness with respect to an outside of the bearing member 60 b. Further, as described above, the pressure of the space 4 formed inside the housing unit 3 varies between, for example, 2 MPa in the high pressure side and 0.5 MPa in the low pressure side 1 a when the cylinders are switched over to the high pressure side 1 b or the low pressure side 1 a. Then, a large pressure difference may be generated between the internal space S of the bearing member 60 and the outer space along with the pressure variation of the space 4. Then, the sealing members 631 b and 632 b may receive large force thereby being deformed. Further, there may increase torque necessary for relatively rotating the inner wheel 61 and the outer wheel 62 by friction caused by contact slide between the inner wheel 61 and the sealing members 631 a and 632 b.

The sealing members 631 and 632 are fixed to the outer wheel 62. A gap G is formed between the inner wheel 61 and the sealing members 631 and 632. With this it is possible to reduce an amount of oil flowing out of the internal space S through the inner wheel 61 and the sealing members 631 and 632. Further, it is possible to reduce the amount of extraneous materials, which are generated from various sliding portions of the GM refrigerator, pass between the inner wheel 61 and the sealing members 631 and 632, and intrude into an internal space S. Further, when the cylinders 11 and 12 are switched to the high pressure side 1 b or the low pressure side 1 a of the compressor 1, it is possible to prevent the sealing members 631 and 632 from deforming due to the pressure variation in the space 4 of the housing unit 3. Further, it is possible to prevent the inner wheel 61 from contacting the sealing members 631 and 632. Further, it is possible to prevent torque necessary for relatively and freely rotating the inner wheel 61 and the outer wheel 62 from increasing.

A value (dimension) GW of the gap G along the radius direction around the rotational axis shaft RA may be preferably 10 to 100 μm. When the gap GW exceeds 100 μm, there is a probability that the amount of a lubricant agent flows out of the internal space S increases or the amount of an extraneous material intrudes inside the internal space S. If the value GW of the width is smaller than 10 μm, airtightness of the internal space S is enhanced. Then, when the cylinders 11 and 12 are connected to the high pressure side 1 b of the low pressure side 1 a of the compressor 1 by the switching operation, there is a probability that the sealing members 631 and 632 deform by pressure variation inside the space 4 of the housing unit 3. When the value GW of the gap is smaller than 10 μm, the inner wheel 61 partly contacts and slides on the sealing members 631 and 632 due to dimension tolerance and so on to thereby increase the torque necessary for mutually and freely rotate the inner wheel 61 and the outer wheel 62.

Portions of the sealing members 631 and 632 facing the inner wheel interposing the gap G are preferably made of a resin. More preferably, the resin is a synthetic rubber such as NBR and ACN (acrylic rubber), fluorine contained resin such as PTFE, or the like. Thus, even if the inner wheel 61 contacts the sealing members 631 and 632 due to dimension tolerance or the like, it is possible to prevent the torque from increasing. Therefore, the value GW of the gap G can be small thereby further reducing the out let flow of the lubricant agent and the mixed amount of the extraneous material. Further, even though the inner wheel 61 partly contacts the sealing members 631 and 632, it is possible to prevent the inner wheel 61 or the like from being damaged. As a result, the life of the bearing member 60 can be elongated.

Although there has been described about the embodiment of the present invention, the present invention is not limited to the above embodiment, and various modifications and changes are possible in a scope of the claims.

AS described above, the sealing members 631 and 632 are fixed to the outer wheel 62, and the gap G is formed between the inner wheel 61 and the sealing members 631 and 632. However, the sealing members 631 and 632 may be fixed to the inner wheel 61 and the gap G may be formed between the sealing members 631 and 632 and the outer wheel 62. Said differently, the sealing members 631 and 632 may be fixed any one of the inner wheel 61 and the outer wheel 62, and the gap G may be formed between the sealing members 631 and 632 and the other one of the inner wheel 61 and the outer wheel 62.

Further, in one or two of the three bearing members 60, 60A and 60B, the sealing members 631 and 632 are fixed to one of the inner wheel 61 and the outer wheel 62, and the gap G is formed between the sealing members 631 and 632 and the other one of the inner wheel 61 and the outer wheel 62.

Accordingly, embodiments of the present invention may provide a novel and useful regenerative type refrigerator solving one or more of the problems discussed above. More specifically, the embodiments of the present invention may provide a regenerative type refrigerator which can reduce the outlet amount of a lubricant agent from an internal space of a bearing member, can reduce a mixed amount of an extraneous material into the internal space of the bearing member, and can prevent deformation of sealing members of the bearing member.

All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the embodiments and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of superiority or inferiority of the embodiments. Although the claims 1-6 have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention. 

1. A regenerative type refrigerator comprising: a cylinder configured to expand a refrigerant gas; a regenerator configured to accumulate cold thermal energy which is generated along with the expansion of the refrigerant gas, the regenerator being provided inside the cylinder so as to be reciprocate inside the cylinder and accommodating a regenerative material inside the regenerator; a rotary drive portion configured to generate driving force for reciprocating the regenerator; a rotary member configured to be rotated by the rotary drive portion; and a bearing member configured to support the rotary member so that the rotary member is rotatable, the bearing member including an inner wheel, an outer wheel, and two sealing members, the inner wheel, the outer wheel and the two sealing members encapsulating a lubricant agent among the inner wheel, the outer wheel and the two sealing members, the outer wheel and the inner wheel being relatively and freely rotatable around a single rotational axis, the two sealing members being respectively provided on sides of the outer wheel and the inner wheel and arranged along the rotational axis, wherein the two sealing members are fixed to one of the inner wheel member and the outer wheel member, and a gap is formed between the two sealing members and another one of the inner wheel member and the outer wheel member.
 2. The regenerative type refrigerator according to claim 1, wherein the two sealing members includes a portion made of a resin and facing the other one of the inner wheel member and the outer wheel member.
 3. The regenerative type refrigerator according to claim 1, wherein the gap is 10 to 100 μm.
 4. The regenerative type refrigerator according to claim 1, wherein the rotary member is a rotational shaft of the rotary drive portion.
 5. The regenerative type refrigerator according to claim 1, further comprising: a scotch yoke, wherein the rotary member is a crank member, wherein the scotch yoke converts rotary drive force of the crank member which is rotated to reciprocating drive force and reciprocating the displacer with the reciprocating drive force, wherein the bearing member is provided in the scotch yoke.
 6. The regenerative type refrigerator according to claim 1, further comprising: a compressor configured to compress the refrigerant gas suctioned from the cylinder and discharge the compressed refrigerant gas to the cylinder, wherein the rotary member is a rotary valve for switching connection of the cylinder to a suction side or a discharge side of the compressor. 